Positive and negative square energies of graphs

A Abiad, L De Lima, DN Desai, K Guo… - arXiv preprint arXiv …, 2023 - arxiv.org
The energy of a graph $ G $ is the sum of the absolute values of the eigenvalues of the
adjacency matrix of $ G $. Let $ s^+(G), s^-(G) $ denote the sum of the squares of the …

On the first two eigenvalues of regular graphs

S Zhang - Linear Algebra and its Applications, 2024 - Elsevier
Let G be a regular graph with m edges, and let μ 1, μ 2 denote the two largest eigenvalues of
AG, the adjacency matrix of G. We show that, if G is not complete, then μ 1 2+ μ 2 2≤ 2 (ω …

Sums of squares of eigenvalues and the vector chromatic number

G Coutinho, TJ Spier - arXiv preprint arXiv:2308.04475, 2023 - arxiv.org
In this short paper we prove that the sum of the squares of negative (or positive) eigenvalues
of the adjacency matrix of a graph is lower bounded by the sum of the degrees divided by …

Extremal values for the square energies of graphs

S Zhang - arXiv preprint arXiv:2409.15504, 2024 - arxiv.org
Let $ G $ be a graph with $ n $ non-isolated vertices and $ m $ edges. The positive/negative
square energies of $ G $, denoted $ s^+(G) $/$ s^-(G) $, are defined as the sum of squares …

Observations on Graph Invariants with the Lov\'asz -Function

I Sason - arXiv preprint arXiv:2310.19169, 2023 - arxiv.org
The Lov\'asz $\theta $-function, originally introduced as an upper bound on the Shannon
capacity of graphs, has many fascinating properties. The first part of this work relies on that …

[PDF][PDF] Observations on graph invariants with the Lovász ϑ-function

I Sason - arXiv preprint arXiv:2310.19169, 2023 - aimspress.com
This paper delves into three research directions, leveraging the Lovász ϑ-function of a
graph. First, it focuses on the Shannon capacity of graphs, providing new results that …

Local Shearer bound

A Martinsson, R Steiner - arXiv preprint arXiv:2501.00567, 2024 - arxiv.org
We prove the following local strengthening of Shearer's classic bound on the independence
number of triangle-free graphs: For every triangle-free graph $ G $ there exists a probability …

Conic programming to understand sums of squares of eigenvalues of graphs

G Coutinho, TJ Spier, S Zhang - arXiv preprint arXiv:2411.08184, 2024 - arxiv.org
In this paper we prove a conjecture by Wocjan, Elphick and Anekstein (2018) which upper
bounds the sum of the squares of the positive (or negative) eigenvalues of the adjacency …

[HTML][HTML] Observations on graph invariants with the Lovász -function

I Sason - AIMS Mathematics, 2024 - aimspress.com
This paper delves into three research directions, leveraging the Lovász $\vartheta $-function
of a graph. First, it focuses on the Shannon capacity of graphs, providing new results that …

A note on the Bollobás-Nikiforov conjecture

J Zeng, XD Zhang - Linear Algebra and its Applications, 2025 - Elsevier
Bollobás and Nikiforov [2] proposed a conjecture that for any non-complete graph G with m
edges and clique number ω, the following inequality holds: λ 1 2+ λ 2 2≤ 2 (1− 1 ω) m …